Identification of errors in transceiver operation, both in transmitter and receiver operation, constitutes an important part when a reliable data transmission is secured in a radio system. Testing a transceiver in a centralized manner allows the radio system to identify such errors.
FIG. 1 illustrates a prior art solution for testing a transceiver. The transceiver comprises a transmitter part 100, a receiver part 102, a joint synthesizer 104 for the transmitter part and the receiver part, a duplex filter 106 for the signal to be transmitted and received and an antenna 108. Another possible alternative is the one in which the transmitter part and the receiver part both comprise a separate synthesizer. The transceiver also comprises a prior art testing implementation in which a test synthesizer 110 is used to generate a signal for testing. The signal is mixed in a mixer 112 with the transmitter part signal, which is connected through a connection 114 to the mixer 112 with the desired power. The result of the mixing is a receiving frequency signal, which is attenuated using an attenuator 116 to a desired power level. The receiving frequency signal is connected through a connection 118 to the receiver part. The transmitter signal and the signal connected to the receiver part are compared to one another in a comparing unit 120 in order to test the transceiver. The comparing unit may be a processor-based testing apparatus such as a computer. In a base station implementation the comparing unit is typically a microcircuit. Furthermore, the prior art solution comprises a software unit 122, which carries out required controls, such as controlling the operation of the test synthesizer 110 and the attenuator 116.
A drawback with the prior art solution is that a separate test synthesizer 110 is required for generating the signal to be mixed with the transmitter part signal. The separate test synthesizer and the complexity of the structure that is required thereof are economically expensive. Another drawback with the prior art solution is that it is difficult to integrate the presented testing implementation to the transceiver, which is a result of the difficulty involved with the integration of the loop filter included in the test synthesizer and the voltage oscillator.